A power supply unit includes: a plurality of batteries each of which has a positive electrode 8 at one end and a negative electrode at the other end; and a bus bar module connecting the batteries in series. The bus bar module includes: a plurality of bus bars each having a pair of connecting parts respectively connected to the electrodes adjacent to each other of the batteries adjacent to each other, and a coupling part coupling the pair of connecting parts to each other; a plurality of terminals each elastically clamping the electrodes and the connecting parts to electrically connect the electrodes to the connecting parts; and a plate to which the bus bars and the terminals are attached. The electrodes are formed in a flat plate shape, and thickness directions of the electrodes which are connected to each other by the bus bar are perpendicular to each other.